The subject matter disclosed herein relates to methanation and, in particular, to heat recovery in a methanation reaction process, integrated with coal gasification process.
Methanation is a physical-chemical process to generate methane from a mixture of various gases out of biomass fermentation or thermo-chemical gasification. The main components are carbon monoxide and hydrogen. Methanation processes require clean synthesis gas (syngas) to be fed to the reactor with a H2 to CO ratio of 3:1. The syngas is typically produced in a gasifier. In the case that syngas is the feed product, methanation may produce synthetic natural gas (SNG).
At present, most methanation processes are isolated processes that include a gasification portion and methanation portion. Typical gasification processes with partial heat recovery produce a syngas with H2 to CO ratio of about 0.95 to 1.0. A catalytic shift reactor is added downstream of the gasifier for shifting CO to H2 ratio. The shifting requires moisturized syngas with a steam-to-dry gas ratio of about 1.1 to 2.2 (varies with type of catalyst efficiency). Traditionally, steam is added to the shift reaction process because the syngas exiting the radiant synthesis gas cooler (RSC) quench doesn't have enough moisture.